TE polarizer based on SOI platform

ABSTRACT

A silicon photonic device includes a silicon-on-insulator substrate, a waveguide, and a plate. The silicon-on-insulator substrate includes a silicon layer and a silicon dioxide layer. The waveguide is disposed on the silicon-on-insulator substrate. The silicon dioxide layer at least partially overlays the waveguide. The plate exhibits metallic characteristics and is at least partially embedded in the silicon dioxide layer of the silicon-on-insulator substrate. The plate is spaced apart from the waveguide and is configured to mitigate transverse magnetic emission propagating through the waveguide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 16/814,825 filed on Mar. 10, 2020, which claimspriority to U.S. patent application Ser. No. 16/389,078 filed on Apr.19, 2019, now issued as U.S. Pat. No. 10,627,574 on Apr. 21, 2020, whichclaims priority to U.S. patent application Ser. No. 16/033,074, filed onJul. 11, 2018, now issued as U.S. Pat. No. 10,310,185 on Jun. 4, 2019,commonly assigned and hereby incorporated by references for allpurposes.

BACKGROUND OF THE INVENTION

The present invention relates to a silicon-photonics device. Moreparticularly, the present invention provides a compact TransverseElectric (TE) polarizer based on silicon-on-insulator (SOI) platform, amethod of making the TE polarizer, and a silicon-photonics circuitintegrated with the TE polarizer for wide band communication in DWDMsystem.

Over the last few decades, the use of broadband communication networksexploded. In the early days Internet, popular applications were limitedto emails, bulletin board, and mostly informational and text-based webpage surfing, and the amount of data transferred was usually relativelysmall. Today, Internet and mobile applications demand a huge amount ofbandwidth for transferring photo, video, music, and other multimediafiles. For example, a social network like Facebook processes more than500 TB of data daily. With such high demands on data and data transfer,existing data communication systems need to be improved to address theseneeds.

Large-scale photonic integrated circuits are becoming very promising formany applications, including next-generation optical networks, opticalinterconnects, dense wavelength division multiplexed (DWDM) systems,coherent transceivers, lab-on-chip, etc. Silicon-based photonicsintegrated circuits have also become very popular, because of theircompatibility with mature CMOS (complementary metal-oxide-semiconductor)technologies with excellent processing control, low cost and high-volumeprocessing. Furthermore, silicon-on-insulator (SOI) is widely used assubstrates for making various silicon-photonics devices. It is wellknown that SOI waveguides are usually severely polarization-sensitive sothat many polarization handling devices including integrated opticalpolarizer have become very important components in polarizationsensitive Si Photonics Circuit.

For example, a compact polarizer made by a simple and high tolerance inprocess on SOI substrate and easy being integrated with othersilicon-photonics devices becomes a crucial component for DenseWavelength Division Multiplexing (DWDM) in C-band or O-band. Priorapproaches of making the polarizer for silicon-photonics are mostlyprocess intolerant, complicated, dimension sensitive, or hard to beintegrated with other silicon-photonics devices.

Therefore, it is desired to develop improved compact, simple,process-robust TE polarizer for easy integrating in silicon-photonicscircuit for wide band DWDM application.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to photonic broadband communicationdevice. More particularly, the present invention provides a compactTransverse Electric (TE) polarizer based on silicon-on-insulator (SOI)platform, a method of making the TE polarizer, and a silicon-photonicscircuit integrated with the TE polarizer for wide band communication inDWDM system. The TE polarizer based on SOI platform can be integratedwithin a silicon-photonics system in wide band DWDM communicationapplication, though other applications are possible.

In modern electrical interconnect systems, high-speed serial links havereplaced parallel data buses, and serial link speed is rapidlyincreasing due to the evolution of CMOS technology. Internet bandwidthdoubles almost every two years following Moore's Law. But Moore's Law iscoming to an end in the next decade. Standard CMOS silicon transistorswill stop scaling around 5 nm, and the internet bandwidth increasing dueto process scaling will plateau. But Internet and mobile applicationscontinuously demand a huge amount of bandwidth for transferring photo,video, music, and other multimedia files. This disclosure describestechniques and methods to improve the communication bandwidth beyondMoore's law.

In an embodiment, the present invention provides a Transverse Electric(TE) polarizer. The TE polarizer includes a silicon-on-insulatorsubstrate having a silicon dioxide layer. The TE polarizer furtherincludes a waveguide embedded in the silicon dioxide layer.Additionally, the TE polarizer includes a plate structure embedded inthe silicon dioxide layer substantially in parallel to the waveguidewith a gap distance. The plate structure induces an extra transmissionloss to a Transverse Magnetic (TM) mode in a light wave travelingthrough the waveguide.

In an alternative embodiment, the present invention provides a methodfor forming a Transverse Electric (TE) polarizer. The method includesproviding a silicon-on-insulator substrate having a silicon dioxidelayer. Additionally, the method includes forming a waveguide embedded inthe silicon dioxide layer. Furthermore, the method includes forming aplate structure embedded in the silicon dioxide layer substantially inparallel to the waveguide with a gap distance. Dimensions of thewaveguide and the plate structure and the gap distance between them aretuned to induce an extra transmission loss to a Transverse Magnetic (TM)mode in a light wave traveling through the waveguide greater than afirst target loss for all wavelengths in a band, and a transmission lossof Transverse Electric (TE) mode in the light wave is smaller than asecond target loss for all wavelengths in the band.

In another alternative embodiment, the present invention provides asilicon-photonics circuit including the TE polarizer integrated with aDWDM system. Optionally, the TE polarizer can be inserted in thesilicon-photonics circuit without disturbing the circuit layout.Optionally, the TE polarizer can be configured to different lengthsaccording to the extinction ratio requirement in particularapplications.

Many benefits of the TE polarizer can be achieved with the presentinvention based on SOI platform. As an example, the SOL platform isfully compatible with CMOS technology, which substantially simplifiesthe process of making the TE polarizer itself as well as integrated itwith other silicon-photonics devices flexibly. High tolerance inmaterial selection and dimensions under a same scope of a simplemanufacture process allows the TE polarizer to be tuned to providedifferent scaled distinction ratio with different compact sizes for widerange of wavelengths either in C-band or O-band for polarizationsensitive DWDM communication system.

The present invention achieves these benefits and others in the contextof disclosed Transverse Electric (TE) polarizer based on a SOIsubstrate. A further understanding of the nature and advantages of thepresent invention may be realized by reference to the latter portions ofthe specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following diagrams are merely examples, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize many other variations, modifications, and alternatives.It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this process andscope of the appended claims.

FIG. 1 is a simplified cross-sectional view of a TE polarizer based onSOI platform according to an embodiment of the present invention.

FIG. 2 is an exemplary diagram of optical transmission loss versuslength of a plate structure with different gap distances from a SiNwaveguide to provide extra loss to Transverse Magnetic mode of a lightwave traveling through the waveguide according to some embodiments ofthe present invention.

FIG. 3 is an exemplary diagram of polarization extinction ratio versuslength of a plate structure with different gap distances from a SiNwaveguide to provide extra loss to Transverse Magnetic mode of a lightwave traveling through the waveguide according to some embodiments ofthe present invention.

FIG. 4 is an exemplary plot of transmission loss for all wavelengths inC-band from 1525 nm to 1565 nm in TE mode and TM mode through the SiNwaveguide according to an embodiment of the present invention.

FIG. 5 is an exemplary diagram of optical transmission loss versuslength of a plate structure with different gap distances from a Siwaveguide to provide extra loss to Transverse Magnetic mode of a lightwave traveling through the waveguide according to some alternativeembodiments of the present invention.

FIG. 6 is an exemplary diagram of polarization extinction ratio versuslength of a plate structure with different gap distances from a Siwaveguide to provide extra loss to Transverse Magnetic mode of a lightwave traveling through the waveguide according to some alternativeembodiments of the present invention.

FIG. 7 is an exemplary plot of transmission loss for all wavelengths inC-band from 1525 nm to 1565 nm in TE mode and TM mode through the Siwaveguide according to an alternative embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to photonic broadband communicationdevice. More particularly, the present invention provides a compactTransverse Electric (TE) polarizer based on silicon-on-insulator (SOI)platform and a method of making the TE polarizer, and asilicon-photonics circuit integrated with the TE polarizer for wide bandcommunication in DWDM system. The TE polarizer based on SOI platform canbe integrated within a silicon-photonics system in wide band DWDMcommunication application, though other applications are possible.

Compact, simple and process tolerant TE polarizer based onsilicon-on-insulator (SOI) is crucial element for handling polarizationsensitive optical transmission of Dense Wavelength Division Multiplexing(DWDM) light wave in C-band or O-band through silicon-photonics circuit.Several existing TE polarizer products have different kinds ofdrawbacks. For example, a TE polarizer based on shallow-etched SOI ridgewaveguide or engineered waveguides leaking unwanted mode to Si substratehas issues being process intolerant. Subwavelength grating Si waveguidepolarizer or hybrid plasmonic Bragg grating based polarizer has verycomplicated grating process. Photonic crystals-based polarizer alsoneeds grating and hard to be integrated with other silicon-photonicscircuits. A Graphene assisted polarizer based on Mach-ZehnderRefractometer (MZR) needs extra material system involved and is not verycompatible with existing CMOS-based silicon-photonics process. Waveguidebased polarizer is compatible with silicon-photonics process but highlydimension sensitive.

This invention provides a SiN/Si based, simple, and robust polarizerdesign in C-band or O-band for integration with silicon-photonicscircuits. There is no extra process step needed other than standard CMOSprocess. The following description is presented to enable one ofordinary skill in the art to make and use the invention and toincorporate it in the context of particular applications. Variousmodifications, as well as a variety of uses in different applicationswill be readily apparent to those skilled in the art, and the generalprinciples defined herein may be applied to a wide range of embodiments.Thus, the present invention is not intended to be limited to theembodiments presented, but is to be accorded the widest scope consistentwith the principles and novel features disclosed herein.

The reader's attention is directed to all papers and documents which arefiled concurrently with this specification and which are open to publicinspection with this specification, and the contents of all such papersand documents are incorporated herein by reference. All the featuresdisclosed in this specification, (including any accompanying claims,abstract, and drawings) may be replaced by alternative features servingthe same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Furthermore, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of” or “act of” in the Claims herein is notintended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

Please note, if used, the labels left, right, front, back, top, bottom,forward, reverse, clockwise and counterclockwise have been used forconvenience purposes only and are not intended to imply any particularfixed direction. Instead, they are used to reflect relative locationsand/or directions between various portions of an object.

FIG. 1 is a simplified cross-sectional view of a TE polarizer based onSOI platform according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, asilicon-on-insulator substrate is provided on which many CMOS processescan be performed for forming various photonics elements includingwaveguides embedded in a silicon dioxide layer. Referring to FIG. 1 , asilicon dioxide layer SiO₂ is overlying a silicon layer Si, and awaveguide 100 is formed with a cross-sectional rectangular shape havinga first width W1 and a first thickness T1. Optionally, the waveguide 100has a first length (along a direction into the cross-section, not shown)embedded inside the silicon dioxide layer SiO₂. Optionally, the firstlength can be an arbitrary value depending on applications. Optionally,the waveguide is made with semiconducting characteristics. Optionally,the semiconducting characteristics include polarization sensitivebirefringence. Optionally, the semiconducting characteristics areprovided by a material of silicon, i.e., the waveguide 100 is a Siwaveguide. Optionally, the semiconducting characteristics are providedby a material of silicon nitride, i.e., the waveguide 100 is a SiNwaveguide. Optionally, the waveguide 100 is made by a standard SiN/Si onSOI single mode waveguide process compatible with CMOS process withoutextra waveguide engineering.

In the embodiment, referring to FIG. 1 , a plate structure 200 is formedwith a second width W2 and a second thickness T2 as shown in thecross-sectional view. Additionally, the plate structure 200 is formedsubstantially in parallel to the waveguide 100 with a gap distance G.Optionally, the plate structure 200 is fully embedded in the silicondioxide layer SiO₂ with a second length (not explicitly shown) beingequal to or smaller than the first length of the waveguide 100.Optionally, the plate structure 200 is made with metalliccharacteristics. Optionally, the metallic characteristics are providedby a material of metal nitride. In an example, the material is TitaniumNitride TiN. In an embodiment, a CMOS foundry TiN deposition process isused for forming the structure. Other metallic materials are possiblereplacement for making the plate structure 200.

In an embodiment, the structure with a cross section shown in FIG. 1 anda length equal to the first length of the waveguide 100 forms a TEpolarizer. The TE polarizer is configured to have the waveguide 100 ofthe first length to contain a light wave with primarily TE modepolarization received at one end of the waveguide 100 and to induceextra loss to TM mode by the plate structure 200 of the second length ata gap distance away from the waveguide 100 so that the light wave isoutputted at the other end with TE-mode in higher extinction ratio. Infact, the TM mode confinement in the SiN/Si single mode waveguide withsemiconducting characteristics is less tight than TE mode. TiN platestructure with metallic characteristics causes much higher absorbingloss to the TM mode of the light wave through the SiN/Si waveguide dueto the evanescent tail.

In an embodiment, the TE polarizer disclosed in this invention issubstantially wavelength insensitive for being integrated in wide bandsilicon-photonics circuits. It can be inserted in a silicon-photonicscircuit without disturbing the circuit layout and causing processincompatibility. In an embodiment, the structure shown in FIG. 1 can beflexibly tuned to optimize shapes and dimensions of the waveguide 100and plate structure 200 to achieve desired TE mode extinction ratio withtransmission loss in TE mode being minimized for a wide band ofwavelengths.

FIG. 2 is an exemplary diagram of optical transmission loss versuslength of a plate structure with different gap distances from awaveguide to provide extra loss to TM mode of a light wave travelingthrough the waveguide according to some embodiments of the presentinvention. Referring to FIG. 2 , the TE polarizer is optimized by tuningthe length (particularly the second length of a plate structure) and thegap distance between the plate structure and the waveguide. In thisexample, the TE polarizer includes a SiN waveguide 100 and a TiN platestructure 200 at a gap distance G. Optionally, the second length of theTiN plate structure 200 disposed at a gap distance G away from the SiNwaveguide 100 is substantially the same as the first length of thewaveguide 100, i.e., the length of the TE polarizer. Curves 1 and 5 arerespective transmission loss for TE mode and TM mode at a gap distanceof a first value G1 (or G5=G1) for the TE polarizer length varied from 0to 1000 μm. Curves 2 and 6 are respective transmission loss for TE modeand TM mode at a gap distance of a second value G2 (or G6=G2) for the TEpolarizer in the same length range. Here G2 (or G6) is smaller than G1(or G5). Curves 3 and 7 are respective transmission loss for TE mode andTM mode at a gap distance of a third value G3 (or G7=G3) for the TEpolarizer in the same length range. Here G3 (or G7) is smaller than G2(or G6). Curves 4 and 8 are respective transmission loss for TE mode andTM mode at a gap distance of a fourth value G4 (or G8=G4) for the TEpolarizer in the same length range. Here G4 (or G8) is smaller than G3(or G7).

In a specific example shown in FIG. 2 , the TE polarizer is providedwith a SiN waveguide 100 being given a width of 0.7 μm and a thicknessof 0.4 μm, and a TiN plate structure 200 being given a width of 2 μm anda thickness of 0.1 μm. The gap distance is selected as following,G1=G5=1.4 μm; G2=G6=1.05 μm; G3=G7=0.75 μm; and G4=G8=0.5 μm. Referringto FIG. 2 , for gap distance G1=G5=1.4 μm; G2=G6=1.05 μm, thetransmission loss for TE mode is very small (<2 dB) for all differentlength values of the TE polarizer up to 1000 μm. More specifically, theloss slightly increases as the length increases. But the transmissionloss for TM mode increases very fast as the length increases. For gapdistance G3=G7=0.75 μm; and G4=G8=0.5 μm, the transmission loss for TEmode increases too fast with increasing length value, which is notpreferable for the TE polarizer.

FIG. 3 is an exemplary diagram of polarization extinction ratio versuslength of a plate structure with different gap distances from awaveguide to provide extra loss to TM mode of a light wave travelingthrough the waveguide according to some embodiments of the presentinvention. Referring to FIG. 3 , curves 9, 10, 11, and 12 are respectivevariations of extinction ratio (ER) versus length up to 1000 μm of theTE polarizer for four different selections of gap distance G, 1.4 μm,1.05 μm, 0.75 μm, and 0.5 μm. ER is found to be substantially linearlyproportional to the length of the TE polarizer (specifically the lengthof TiN plate structure embedded in the silicon dioxide layer). Forexample, for G2=1.05 μm, a TE polarizer with a length of 250 μm yieldsan ER>10 dB for TE/TM mode through the waveguide. In another example,for G1=1.4 μm, a TE polarizer of 200 μm yields an ER^(˜)2 dB for TE/TMmode through the waveguide.

FIG. 4 is an exemplary plot of transmission loss for all wavelengths inC-band from 1525 nm to 1565 nm in TE mode and TM mode through thewaveguide according to an embodiment of the present invention. For aspecifically given dimensions of a TE polarizer described herein with agap distance G=1.05 μm and the length of TiN plate structure, thetransmission losses through the SiN waveguide for TE mode as well as forTM mode are plotted for all wavelengths in a wide band from 1525 nm to1565 nm. This is fairly desired TE polarizer for C-band with TE losssmaller than 1 dB very much independent of the wavelength while yieldingTM loss greater than 10 dB yet still very insensitive to variation ofthe wavelength.

In another embodiment, the TE polarizer includes a Si waveguide 100 anda TiN plate structure 200 at a gap distance G. Optionally, the secondlength of the TiN plate structure 200 disposed at a gap distance G awayfrom the SiN waveguide 100 is substantially the same as the first lengthof the waveguide 100, i.e., the length of the TE polarizer. FIG. 5 is anexemplary diagram of optical transmission loss versus length of a platestructure with different gap distances from a waveguide to provide extraloss to Transverse Magnetic mode of a light wave traveling through thewaveguide according to some alternative embodiments of the presentinvention. Curves 13 and 16 are respective transmission loss for TE modeand TM mode at a gap distance of a first value G13 (or G16=G13) for theTE polarizer length varied from 0 to 1000 μm. Curves 14 and 17 arerespective transmission loss for TE mode and TM mode at a gap distanceof a second value G14 (or G17=G14) for the TE polarizer in the samelength range. Here G14 (or G17) is smaller than G13 (or G16). Curves 15and 18 are respective transmission loss for TE mode and TM mode at a gapdistance of a third value G15 (or G18=G15) for the TE polarizer in thesame length range. Here G15 (or G18) is smaller than G14 (or G17).

In a specific example shown in FIG. 5 , the TE polarizer is providedwith a Si waveguide 100 being given a width of 0.45 μm and a thicknessof 0.22 μm, and a TiN plate structure 200 being given a width of 2 μmand a thickness of 0.1 μm. The gap distance is selected as following,G13=G16=1.0 μm; G14=G17=0.8 μm; and G15=G18=0.6 μm. Referring to FIG. 5, for all three choices of gap distance, the TE losses are all verysmall for the length of TE polarizer up to 1000 μm. At the same time,the TM losses become fairly large (>5 dB at length of ^(˜)800 μm) forG14=G17=0.8 μm and even bigger (>10 dB at length of ^(˜)300 μm) forG15=G18=0.6 μm.

FIG. 6 is an exemplary diagram of polarization extinction ratio versuslength of a plate structure with different gap distances from awaveguide to provide extra loss to Transverse Magnetic mode of a lightwave traveling through the waveguide according to some alternativeembodiments of the present invention. FIG. 6 is an alternate plot ofFIG. 5 to show the extinction ratio of TE/TM for the light wavetraveling through the Si waveguide 100 with a TiN plate structure 200set aside. Curve 19 corresponds to a gap distance G19=G13=1.0 μm; Curve20 corresponds to a smaller gap distance G20=G14=0.8 μm; and Curve 21corresponds to an even smaller gap distance G21=G15=0.6 μm.

FIG. 7 is an exemplary plot of transmission loss for all wavelengths inC-band from 1525 nm to 1565 nm in TE mode and TM mode through thewaveguide according to an alternative embodiment of the presentinvention. For a specifically given dimensions of a TE polarizerdescribed herein with a gap distance G=0.8 μm and the length of TiNplate structure, the transmission losses through the Si waveguide for TEmode as well as for TM mode are plotted for all wavelengths in a wideband from 1525 nm to 1565 nm. This is fairly desired TE polarizer forC-band with TE loss smaller than 1 dB very much independent of thewavelength while yielding TM loss greater than 7 dB yet very muchinsensitive to variation of the wavelength.

In another aspect, the present disclosure provides a method of making aTE polarizer based on SOI platform. Referring to FIG. 1 , the methodincludes providing a silicon-on-insulator substrate having a silicondioxide layer SiO₂ (on top of a silicon layer Si). The SOI substrate iscommonly used for fabrication and integration of silicon-photonicscircuits to form various kinds of SiPho devices for applicationsincluding data communication in a DWDM system with wide bandwavelengths. Particularly, TE polarizer is a widely used device inpolarization sensitive Si Photonics Circuit. Additionally, the methodincludes forming a waveguide embedded in the silicon dioxide layer andforming a plate structure embedded in the silicon dioxide layersubstantially in parallel to the waveguide with a gap distance. Theseprocesses are fully compatible to existing CMOS-based process for makingsilicon-photonics circuits on the SOI substrate without complicatewaveguide engineering. The plate structure, which may be based on TiN orother materials with metallic characteristics, also can be made by COMSfoundry (TiN) deposition process.

In an embodiment, the method is implemented by tuning dimensions of thewaveguide and the plate structure and the gap distance between them tooptimize the performance of the TE polarizer. In particular, the methodincludes using the plate structure to induce an extra transmission lossto a Transverse Magnetic (TM) mode in a light wave traveling through thewaveguide greater than a first target loss for all wavelengths in aband, and a transmission loss of Transverse Electric (TE) mode in thelight wave is smaller than a second target loss for all wavelengths inthe band.

In an embodiment, the step of forming of the waveguide includes forminga first length and a rectangular shaped cross section having a firstwidth and a first thickness using a material with semiconductingcharacteristics. Optionally, the semiconducting characteristics includematerial of silicon or silicon nitride or other materials compatiblewith silicon-photonics process.

In the embodiment, the step of forming of the plate structure includesforming a second length, a second width, and a second thickness using amaterial with metallic characteristics. Additionally, the step includesoptimizing the gap distance between the plate structure and thewaveguide. Further the step includes optimizing the second length, whichcan be smaller than or equal to the first length. Optionally the secondwidth is set to be greater than the first width and the second thicknessis set to be smaller than the first thickness.

In the embodiment, the step of optimizing of the gap distance includesmaking the transmission loss of the Transverse Magnetic (TM) mode in thelight wave for all wavelengths in C band from 1525 nm to 1565 nm greaterthan the first target loss selected from 5 dB, 7 dB, 10 dB, and 12 dBand the transmission loss of Transverse Electric (TE) mode in the lightwave for all wavelengths in C band smaller than the second target lossselected from 2 dB, 1.5 dB, 1 dB, 0.5 dB.

Optionally, the method further includes increasing the second lengthfrom a value of smaller than 200 μm, smaller than 250 μm, smaller than300 μm, smaller than 500 μm, smaller than 750 μm, smaller than 1 mm todecide a practical length of a TE polarizer that yields a properextinction ratio for specific applications. Optionally, the length ofthe TE polarizer is a substantially linearly proportion to theextinction ratio.

In yet another aspect, the present disclosure provides asilicon-photonics circuit for DWDM communication system containing theTransverse Electric polarizer based on SOI platform. Optionally, thesilicon-photonics circuit includes passive components like multiplexeror demultiplexer, polarization rotator, polarization splitter, etc.Optionally, the silicon-photonics circuit includes components likemodulator, coupler, phase shifter etc. that are coupled to activedevices (laser or photodetector) for transmitting or receiving opticalsignals in a wide band. Optionally, the wide band can be C-band from1525 nm to 1565 nm. Optionally, the wide band can be O-band from 1270 nmto 1330 nm. The TE polarizer described herein can be optimized to have atransmission loss of Transverse Magnetic (TM) mode in the light wave forall wavelengths in the O-band to be greater than a first target loss anda transmission loss of Transverse Electric (TE) mode in the light wavefor all wavelengths in the band to be smaller than a second target loss.Optionally, the first target loss is selected from one of 5 dB, 7 dB, 10dB, and 12 dB for all wavelengths in O-band from 1270 nm to 1330 nm, andthe second target loss is selected from one of 2 dB, 1.5 dB, 1 dB, 0.5dB for all wavelengths in the O-band. Optionally, the TE polarizer canbe inserted in the silicon-photonics circuit without disturbing thecircuit layout. Optionally, the TE polarizer can be configured todifferent length according to the extinction ratio requirement inparticular application.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A silicon photonics device comprising: a silicon-on-insulator substrate including a silicon layer and a silicon dioxide layer; a waveguide disposed on the silicon-on-insulator substrate, the silicon dioxide layer at least partially overlaying the waveguide; and a plate exhibiting metallic characteristics at least partially embedded in the silicon dioxide layer above the waveguide, the plate being wider than the waveguide, spaced apart from the waveguide, and configured to induce an increased transmission loss of a transverse magnetic mode in a light wave propagating through the waveguide.
 2. The silicon photonics device of claim 1 wherein the waveguide includes material exhibiting semiconductor characteristics.
 3. The silicon photonics device of claim 1 wherein the plate is disposed parallel to the waveguide.
 4. The silicon photonics device of claim 1 wherein the plate induces a transmission loss greater than or equal to a target transmission loss in the light wave propagating through the waveguide in the transverse magnetic mode.
 5. The silicon photonics device of claim 1 wherein the plate induces a transmission loss less than or equal to a target transmission loss in the light wave propagating through the waveguide in a transverse electric mode.
 6. The silicon photonics device of claim 1 wherein the waveguide and the plate have dimensions corresponding to a polarization extinction ratio.
 7. The silicon photonics device of claim 1 wherein dimensions of the waveguide and the plate are configured to increase a transmission loss in the transverse magnetic mode and to minimize a transmission loss in a transverse electric mode.
 8. The silicon photonics device of claim 1 wherein the plate has different thickness than the waveguide.
 9. A silicon photonics device comprising: a silicon-on-insulator substrate including a silicon layer and a silicon dioxide layer; a waveguide disposed on the silicon-on-insulator substrate, the silicon dioxide layer at least partially overlaying the waveguide; and a plate exhibiting metallic characteristics at least partially embedded in the silicon dioxide layer of the silicon-on-insulator substrate, the plate spaced apart from the waveguide and configured to induce an increased transmission loss of a transverse magnetic mode in a light wave propagating through the waveguide, wherein the waveguide comprises silicon or silicon nitride and wherein the plate comprises a metal nitride.
 10. The silicon photonics device of claim 1 further comprising a dense wavelength division multiplexing circuit coupled to the waveguide for transmitting the light wave in C-band or O-band.
 11. The silicon photonics device of claim 10 wherein the silicon photonics device and the dense wavelength division multiplexing circuit are fabricated using a complementary metal-oxide-semiconductor process.
 12. The silicon photonics device of claim 1 wherein the waveguide comprises silicon or silicon nitride and wherein the plate comprises a metal nitride.
 13. The silicon photonics device of claim 9 wherein the plate is disposed parallel to the waveguide.
 14. The silicon photonics device of claim 9 wherein the plate induces a transmission loss greater than or equal to a target transmission loss in the light wave propagating through the waveguide in the transverse magnetic mode.
 15. The silicon photonics device of claim 9 wherein the plate induces a transmission loss less than or equal to a target transmission loss in the light wave propagating through the waveguide in a transverse electric mode.
 16. The silicon photonics device of claim 9 wherein the waveguide and the plate have dimensions corresponding to a polarization extinction ratio.
 17. The silicon photonics device of claim 9 wherein dimensions of the waveguide and the plate are configured to increase a transmission loss in the transverse magnetic mode and to minimize a transmission loss in a transverse electric mode.
 18. The silicon photonics device of claim 9 wherein the plate has different dimensions than the waveguide.
 19. The silicon photonics device of claim 1 wherein the plate induces a transmission loss in the transverse magnetic mode that is greater than a transmission loss in a transverse electric mode.
 20. The silicon photonics device of claim 9 wherein the plate induces a transmission loss in the transverse magnetic mode that is greater than a transmission loss in a transverse electric mode. 